Why is there more matter than antimatter? Neutrinos may be the answer

Hyperaxion Mar 8, 2020

A theory put forward by astrophysicists at the University of California at Berkeley, USA, may explain why the Universe did not annihilate itself shortly after the Big Bang.


According to the theory, shortly after the Big Bang, the Universe underwent a dramatic expansion and this process led to the transformation of energy into matter. However, scientists believe, the same amount of matter and antimatter would have formed at this stage, and, as you may know, the two destroy each other as soon as they meet.

Matter and antimatter destroy each other as soon as they meet
(Credit: The Daily Galaxy).

This means that billions and billions of years ago, when the Universe was still a baby, matter and antimatter should have disappeared – before galaxies, stars, planets and everything else in the cosmos emerged. In fact, following this same reasoning, space itself should have collapsed.

Read more: Terraforming Mars – Can we do it?

Except that’s not what happened, since the Universe is home to an abundant amount of matter – including us humans! – and, although antimatter is present in the cosmos, as far as we know, there is much more conventional matter.

But why?

And more: what caused this imbalance between the two and what happened to the antimatter, if it didn’t come across the matter and annihilated with it?


Matter and antimatter destroy each other because, despite being identical, they have opposite electrical charges. The same can be said about other fundamental particles described in the Standard Model, such as the electron/positron and proton/antiproton, for example.

But there are also particles with a neutral charge that, according to theories – and depending on conditions -, could behave like their own antiparticles.

Neutrinos could behave like their own antiparticles
(Credit: Space.com).

An example is neutrinos, particles theoretically described by the Austrian physicist Wolfgang Pauli in the 1930s and observed directly in the 1950s through the Cowan-Reines Experiment.

Astrophysicists believe that neutrinos may have had something to do with the mystery about the difference between the amount of matter and antimatter in the Universe.

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According to the researchers, a few million years after the Big Bang, the cosmos suffered a strong cooling and went through what scientists call the “phase transition” – something similar to what happens when water freezes and changes from liquid to solid.

It turns out that some particles, when subjected to certain temperatures, change their behavior, and what astrophysicists suggest is that this phase transition caused tubes made up of magnetic fields or cosmic filaments to appear. Going back to the analogy of freezing water, think of the cracks that appear in the ice in certain situations. Well, something like that.

Tubes made up of magnetic fields or cosmic filaments may have appeared as the universe cooled down
(Credit: New Atlas).

According to some theories, these filaments permeate the cosmos – and are an integral part of String Theory – and astrophysicists think that they were responsible, along with the cooling that happened during the phase transition, for the change in neutrino behavior, causing it to have a positive charge and switching to the side of matter, leaving antimatter at a disadvantage.

Cosmic challenge

The challenge is that, to prove that this theory is correct, researchers would have to demonstrate it, and the space observatories and telescopes we use today only allow scientists to observe the Universe’s past to a certain extent.

However, the team believes that the filaments formed during the phase transition created small ripples in the space-time fabric and, if they are correct, they may find a way to detect them.

Filaments created during the phase transition created small ripples in the space-time fabric.
(Credit: New Atlas).

Astrophysicists believe that the disturbances will be incredibly discrete, but it may be that the technology currently used to detect gravitational waves – which are formed when massive stars collide or black holes merge, for example – can be improved, to identify the ripples left by the filaments.

In addition, there are several observatories, telescopes and other equipment under development that will soon start operating and, who knows, may be used in the search for ripples. And if they are discovered, astrophysicists will have found the answer to one of cosmology’s greatest mysteries.


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